Supplemental Members are listed in the NADCA Membership Directory and receive all membership benefits, except that Supplemental Members are ineligible to vote. Supplemental Members must have a NADCA-certified ASCS on staff, hold minimum general liability insurance coverage of $500,000, as well as hold any applicable state licenses that may be required in the state you operate for duct cleaning and/or cutting access holes into a system. One individual cannot serve as the certified ASCS for more than one location.